BMCs and Alternators

[StephenA]

Ever since we got the BMC back in 1985 its alternator configuration has always been problematical and to be honest its made going on holiday a bit of a pain as it eats belts and doesn't charge properly after a few days as the belts have either stretched or have worn away.

 

The engine was obviously fitted originally with an dynamo. There are two pulley on the end of the crank - a big one which drives the water pump (and the alternator) and a smaller one which does nothing at all.

 

For the second time in 10 years the Alternator has thrown itself and taken the waterpump bracket out (which idiot decided to bolt an alternator to a bracket on a waterpump made from grotty alloy I do not know).

 

Some of the problem with the belts being eaten is that I'm sure the waterpump pulley is actually slightly eccentric/warped so it chafes the belt.

 

So are there any after market kits that we can get that will allow us to use a 60amp alternator, that preferably doesn't involve bolting anything to the water pump If it involves dropping the pulleys off the crank and putting new ones then so be it.

[John Orentas]

Hi Stephen.

 

This matter of alternators and belt eating has come up many times on the forum, start by doing a search of past posts.

[StephenA]

I've tried lots of combinations of searches before I posted trying to see if anyone had an answer.

 

As I've got :

a) a broken water pump bracket (and thus will need to replace the water pump)

a continual problem with belt wear (which I suspect is down to not having the right profile belt or a belt made of the right material)

c) an eccentric/wobbly water pump pulley

 

It sort of seems sensible to get everything right from the ground up rather than replacing the water pump (there is more than one type - different lengths of pulley shaft) and the pulley and then finding out that actually what i needed was a new (different) pump, with a different pulley (I've seen double grooved ones) and a different alternator...

 

I assume people out there are successfully running 60Amp alternators off an "original" BMC 1.5

Edited May 30, 2007 by StephenA

[John Orentas]

Hi Stephen.

 

The premature belt wear issue: The general consensus was that if you go out of your way to get a good quality belt you will get much longer life, Halfords products was mentioned by several people, important to to get the correct profile as there are two distinct types. My own view is that people also tend to use belts which are too narrow for the pulleys, the correct size will protrude from the diameter of the pulley by a couple of millimetres.

 

Bear in mind too that boat alternators work harder than vehicle types so you may expect shorter life and more frequent adjustment, an out of adjustment belt will have a very much reduced life. Boat engine compartment will inevitably will be much hotter so pay regard to to ventilation of the area around the drive belts. In your case, having slightly unusual mountings and a bit of history you should pay special regard to having totally compatible pulleys and the alignment of them.

 

It sounds like your alternator would benefit from a new beefed up mounting, never as difficult as it sounds, could you sketch something out and get someone to make one.

[Sir Nibble]

My BMC runs a 65A alternator no problem. I suspect your knackered pulley could be the problem, change it. If the pulley is eccentric there will be a fluctuating side loading on the alternator which is very likely the cause of your problem. If it is not too much hassle it would help if you could fit a larger pulley to minimise the torque loading, (I know that seems odd, but trust me on that!).

[StephenA]

Hi Stephen.

 

The premature belt wear issue: The general consensus was that if you go out of your way to get a good quality belt you will get much longer life, Halfords products was mentioned by several people, important to to get the correct profile as there are two distinct types. My own view is that people also tend to use belts which are too narrow for the pulleys, the correct size will protrude from the diameter of the pulley by a couple of millimetres.

 

We are using Halfords HB1013a (or is it b?) Its the only belt that is the right length.

 

Bear in mind too that boat alternators work harder than vehicle types so you may expect shorter life and more frequent adjustment, an out of adjustment belt will have a very much reduced life. Boat engine compartment will inevitably will be much hotter so pay regard to to ventilation of the area around the drive belts. In your case, having slightly unusual mountings and a bit of history you should pay special regard to having totally compatible pulleys and the alignment of them.

Which is the reason I asked here about mountings. Belt life is sometimes months (the current one has been once since Easter and has only been adjusted once and is charging quite well considering the front bracket is sheared) but has been known to be weeks (I think last year we got through one in less than a week.

 

It sounds like your alternator would benefit from a new beefed up mounting, never as difficult as it sounds, could you sketch something out and get someone to make one.

 

I'm sure it would - I'm trying to work out (from memory) if there is any way to mount the alternator without having to use the water pump bracket..

 

If only it was all self adjusting and reliable like the serpertine belt on my Saab ;-)

[John Orentas]

We are using Halfords HB1013a (or is it b?) Its the only belt that is the right length.

 

 

Remember also that a good source of drive belts is companies that do industrial power transmissions, I talked my way into Fenners place in Manchester once.

[David Schweizer]

I have a 55 amp alternator on my 1981 BMC 1.5, and because I also have a Sterling Advanced Alternator regulator, it is often pumping out 40 to 50 amps. I have never had a belt fail on me, although getting the tension correct can occassionally be a problem. I have had one alternator fail on me in ten years, but that was caused primarily by the accumulation of oil deposits inside the alternator from a smokey engine, rather than over working.

 

The engine has since been re-built is no longer smokey, however the engineer did point out tht he had fitted a cast Iron water pump, not an alloy one, as he had found that these can fail prematurely. It also has an iron sliding clamp, although the bracket does appear to be alloy. one thing that occures to me is have you checked the alignment? When I recently fitted the replacement Alternator, failed to check this and the belt did start to shed a lot of black dust. Uopon checking I determined that the new unit was out of line and had to adjust the bushes on the alternator and insert a couple of washers to re-align everything. It has been OK since.

 

If the altermnator is not out of alignment, it may well be that a worn pump pulley is contributing to the problems you have, or maybe the belt is not the correct one, the belt on my engine has a Lucas part Number which can probably be cross referenced, it is Part No. Lucas KDB 105 (9.5 x 1050).

Edited May 30, 2007 by David Schweizer

[Sir Nibble]

Halfords HB1013a

Right let's see. HB, Halfords belt? 1013, the size of the belt around its circumference in mm. a, It's an "A" type belt, the most common profile in car applications.

So, if you go into a motor factors and ask for a 1013 A type belt, you should get one, or more likely a 1015 which should fit.

[David Schweizer]

Right let's see. HB, Halfords belt? 1013, the size of the belt around its circumference in mm. a, It's an "A" type belt, the most common profile in car applications.

So, if you go into a motor factors and ask for a 1013 A type belt, you should get one, or more likely a 1015 which should fit.

I am wondering whether Stephen has been fitting the wrong sized belt. at that size it must be very tight and difficult to fit (unless the pump or alternator has an undersize pulley) As I have already indicated I have always used a 1050 belt with no problems, and if you check in the Chandleries, I am certain that is the size they sell for the BMC 1.5.

 

ASAP sell a range of Alternator belts including several options for the BMC 1.5, it may be worth contacting them for advice, I have always found them very helpful.

[StephenA]

A 1050 would just fall off

 

The 1013 slips on easily with the alternator pushed all the way down.

 

By the time the belt is worn out the alternator is up as far as it will go (if it swings up any more it hits the heater plug on the end cylinder)

 

The Alternator has a standard pulley on it and the water pump pulley looks totally standard.

 

Its been such a long time since I looked at another BMC closely that I can't state for sure that the large pulley on the crank is the right size.

 

Which all points at the alternator mounting being wrong.

 

Which is why I came on here and asked the question in the first place.

[David Schweizer]

.....As I've got :

a) a broken water pump bracket (and thus will need to replace the water pump)

a continual problem with belt wear (which I suspect is down to not having the right profile belt or a belt made of the right material)

c) an eccentric/wobbly water pump pulley

I have just re-read this statement. Working from memory and looking at the Illustrations in the Workshop manual, I cannot see how the alternator can be held in firmly place whilst under belt pressure. If the Waterpump mounting bracket has been sheared, surely you are not relying solely on the back bracket which is bolted to the crankcase? it must be under tremendous strain, and must have a lot of lateral movement. Get the waterpump replaced (with a Cast Iron one - not Alloy) and you problems may well dissapear.

[StephenA]

With the flange on the waterpump sheared the alternator is currently being held in place by the rear steel bracket (which is secured by three bolts to the cylinder block) and the tensioning strut. The connection to the water pump is currently only staying in alignment as everything else is bolted tight. Obviously this is not a good situation to be in which is why I'm going to fix it - once I've worked out the correct configuration..

 

I've never seen anything but alloy water pumps for the BMC and do they come in the right shaft length (which is something that has caught us out in the past - one pump we got had a shorter shaft on it so the pulley didn't line up with the crank pulley).

[Sir Nibble]

Which all points at the alternator mounting being wrong.

 

Which is why I came on here and asked the question in the first place.

 

If, as you state, the crankshaft pulley is eccentric; then as the pulley turns it tightens and slackens at engine speed. This will set up an oscillation in the side thrust on the alternator and its mounting. It's not surprising if it breaks. Similarly, the belt is being wedged tight into the pulley and then wrenched free at the same rate, of course it will wear.

[David Schweizer]

With the flange on the waterpump sheared the alternator is currently being held in place by the rear steel bracket (which is secured by three bolts to the cylinder block) and the tensioning strut. The connection to the water pump is currently only staying in alignment as everything else is bolted tight. Obviously this is not a good situation to be in which is why I'm going to fix it - once I've worked out the correct configuration..

 

I've never seen anything but alloy water pumps for the BMC and do they come in the right shaft length (which is something that has caught us out in the past - one pump we got had a shorter shaft on it so the pulley didn't line up with the crank pulley).

I cannot answer your question about shaft length, but try these people, they are marine engine specialists:- http://www.lancingmarine.com/bargains.html

[StephenA]

No - crankshaft pulley is not eccentric

 

Its the water pump pulley that would seem to be out of shape. It seems flat if you lay it on a flat surface but when its on the pump there seems to be some movement in the belt path (the sort of movement you'd expect if the pulley was bent)

[David Schweizer]

No - crankshaft pulley is not eccentric

 

Its the water pump pulley that would seem to be out of shape. It seems flat if you lay it on a flat surface but when its on the pump there seems to be some movement in the belt path (the sort of movement you'd expect if the pulley was bent)

 

Ok here is a little test. Run the engine at idle speed and look carefully at the pulley. Is there any detecable movement in the pulley? if there does appear to be movemment take a rod of wood ( a pencil will do) and rest it against a firm surface, slowly move the end of the piece of wood towards the pulley face until it just touches, then back it off a little. Any distortion of the pulley will be demonstrated by the piece of wood touching and then not touching as the pulley rotates. WARNING be very carefull not to get the piece of wood (or anything else) caught in the pulley or belt. If there is movement in the pulley and the surface is flat, either the hole in the centre is out of line(very unlikely) or the pulley shaft is bent which means a new, or re-built pump.

 

edited to include; or the pulley hole is oversize and causing the pulley to move on the shaft

 

If no movement can be detected in the pulley, then any visible distortion of the belt is probably being caused by misalignment. The quickest way to check this is to remove the belt and lay a steel straight edge across the pump pulley and the alternator pulley. Allowing for any variation in the thickness of the two pulleys, it should be possible to detect any mis alignment. If there is misalignment, depending on the type of alternatior you have, this is normally rectified by either adjusting the spacing bushes already installed in the alternator, and/or the addition or removal of spacing washers.

 

Even the smallest degree of misalignment will cause the edge of the belt to rub against the side of the pulley and wear, this is easily detected by the anount of black dust it generates, some of which will be drawn into the alternator and potentially shorten it's life.

Edited May 31, 2007 by David Schweizer

[David Schweizer]

Just found these people who supply spares for BMC tractors. As far as i know the power unit for the 1500 tractor is the same as the BMC 1.5 diesel engine.

 

 

http://www.bmcminitractor.co.uk/html/spares.html

[StephenA]

Thanks for the info David

 

Am away from the boat at the moment so cant check the pulleys easily.

 

I seem to remember putting the pulley on the new pump last time and spinning it and seeing a slight wobble - but as we were stuck in the middle of nowhere at the time I think we probably ignored it.

 

The comments about the length of the belt puzzled me - there is no way on our engine that anything much longer that a 1013 can be used due to the closeness of the alternator to the heater plug... is this the same on other peoples engines or is there something wrong?

[Sir Nibble]

The comments about the length of the belt puzzled me - there is no way on our engine that anything much longer that a 1013 can be used due to the closeness of the alternator to the heater plug... is this the same on other peoples engines or is there something wrong?

 

It does sound odd. You suggested that your engine may have originally had a dynamo, perhaps the job of modifying the mountings may be less than satisfactory?

[John Orentas]

It does sound odd. You suggested that your engine may have originally had a dynamo, perhaps the job of modifying the mountings may be less than satisfactory?

 

 

This engine design has been around in various guises since before the last war, fitted in vans, taxis and anything else you can think of. It would be surprising if there not detail modifications along the way especially with the ancillary components.

[StephenA]

We're pretty sure it had a dynamo, or something else bolted on to the front that used the small (7 inch?) pulley on the front of the crank.

 

The engine has a bell housing with feet (which is great when it comes to doing work on the gear box) and apparently has an "industrial" flywheel.

 

So wherever it came from it didn't come directly out of a vehicle before being put in a boat.

[RobinJ]

Ever since we got the BMC back in 1985 its alternator configuration has always been problematical and to be honest its made going on holiday a bit of a pain as it eats belts and doesn't charge properly after a few days as the belts have either stretched or have worn away.

 

The engine was obviously fitted originally with an dynamo. There are two pulley on the end of the crank - a big one which drives the water pump (and the alternator) and a smaller one which does nothing at all.

 

For the second time in 10 years the Alternator has thrown itself and taken the waterpump bracket out (which idiot decided to bolt an alternator to a bracket on a waterpump made from grotty alloy I do not know).

 

Some of the problem with the belts being eaten is that I'm sure the waterpump pulley is actually slightly eccentric/warped so it chafes the belt.

 

So are there any after market kits that we can get that will allow us to use a 60amp alternator, that preferably doesn't involve bolting anything to the water pump If it involves dropping the pulleys off the crank and putting new ones then so be it.

 

You don't say which engine it is?

The small pulley is for fitting the Jabasco water pump for oil cooler (usually raw water).

The Alternator normally fits on the side of the engine next to the thermostat, secured with a hinge bolt at the top and an adjuster at the bottom. These normally include spacers which allow the alternator pulley to be lined up with the crank and water pump (the right size of washers can be used if necessary). The hinge bolt is normally fixed directly to the block, but it sounds as though in your case it is not - modification?

It is important for long service that the alternator is secured by its rear mounting hole, this may be what is causing the failure, as the alternator will tend to wobble if not!

Many BMC's are fitted with oversize crank pulleys to increase cooling at low revs., this means belt sizes can vary!

I upgraded my alternator to a 70 after a few of the Lucas A127's failed, needed new belt, spacer adjustment and change to electrical connectors (3 pin plug to eyelets).